#include <SPI.h>
#include <MFRC522.h>
#include <SD.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

#define CS_RFID 10
#define CS_TF   8
#define RST_PIN 9
#define LED_PWM 3
#define LED_HB  5

MFRC522 rfid(CS_RFID, RST_PIN);
LiquidCrystal_I2C lcd(0x27, 16, 2);
File logFile;

volatile bool bat_lemah = false;

void setup() {
  pinMode(CS_RFID, OUTPUT);
  pinMode(CS_TF, OUTPUT);
  pinMode(LED_PWM, OUTPUT);
  pinMode(LED_HB, OUTPUT);
  
  digitalWrite(CS_RFID, HIGH);
  digitalWrite(CS_TF, HIGH);

  Serial.begin(9600);
  SPI.begin();
  rfid.PCD_Init();
  
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Sistem Aktif");

  if (!SD.begin(CS_TF)) {
    Serial.println("ERR: SD Init");
    while (1);
  }

  // T2 Fast PWM
  TCCR2A = (1 << COM2B1) | (1 << WGM21) | (1 << WGM20);
  TCCR2B = (1 << CS22);
  OCR2B = 15; 

  // T1 Overflow
  TCCR1A = 0;
  TCCR1B = (1 << CS12) | (1 << CS10); 
  TIMSK1 |= (1 << TOIE1);

  // Analog Comp (1.1V Bandgap vs AIN1)
  ACSR = (1 << ACBG) | (1 << ACIE) | (1 << ACIS1) | (1 << ACIS0); 
  
  sei();
}

ISR(TIMER1_OVF_vect) {
  digitalWrite(LED_HB, !digitalRead(LED_HB));
}

ISR(ANALOG_COMP_vect) {
  bat_lemah = (ACSR & (1 << ACO));
}

void loop() {
  if (bat_lemah) {
    OCR2B = 255; 
    lcd.setCursor(0, 1);
    lcd.print("BAT: LEMAH!     ");
  } else {
    OCR2B = 15;  
    lcd.setCursor(0, 1);
    lcd.print("BAT: AMAN       ");
  }

  digitalWrite(CS_TF, HIGH);
  digitalWrite(CS_RFID, LOW);

  if (!rfid.PICC_IsNewCardPresent() || !rfid.PICC_ReadCardSerial()) return;

  String uidStr = "";
  for (byte i = 0; i < rfid.uid.size; i++) {
    uidStr += String(rfid.uid.uidByte[i] < 0x10 ? "0" : "");
    uidStr += String(rfid.uid.uidByte[i], HEX);
  }
  uidStr.toUpperCase();

  OCR2B = 255; 
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("UID: " + uidStr);

  digitalWrite(CS_RFID, HIGH);
  digitalWrite(CS_TF, LOW);

  logFile = SD.open("log.txt", FILE_WRITE);
  if (logFile) {
    logFile.println(uidStr);
    logFile.close();
    Serial.println("LOG_OK: " + uidStr);
  } else {
    Serial.println("LOG_ERR");
  }

  delay(1000); 
  rfid.PICC_HaltA();
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Sistem Aktif");
}